Ok if its a credits meter that makes sense. I have heard a slight pop like a reply on demo man but weaker, Do the EM's have a snapping reply too or is something going on my machine? when I start a game it will subtract a number from the center number in the balloon. I actually assumed it wasn't a reply as im not a great player and I seem to accumulate free plays on the machine anyway. Maybe EM's required less skill or im just getting lucky?

If anyone was wondering its pop bumper related. You hit the pop bumpers enough times and it will Light. Not sure the exact fine details. Its the kind of extra ball that toggles on and off as you hit bumpers.